Conventionally, to open and close left and right front parts of clothes, a slide fastener including a separable bottom end stop is used in many cases. For example, as a slide fastener mainly used for a long coat and a ski wear, for example, there is known a slide fastener capable of separating left and right rows of elements in an engaged state from not only one end (an upper end) of a fastener chain but also from the other end (a lower end) of the fastener chain, to increase functionability and designability of clothes. The slide fastener capable of separating the rows of elements in the engaged state from both ends is also called a reverse-opening slide fastener.
An example of the reverse-opening slide fastener is disclosed in Japanese Patent Application Laid-Open No. 2009-95425 (Patent Document 1).
As shown in FIGS. 15 and 16, a slide fastener 101 described in Patent Document 1 includes a pair of left and right fastener stringers 102 having rows 103 of elements, a box pin 104 arranged on the right fastener stringer 102, an insert pin 105 arranged on the left fastener stringer 102, and a first slider (a lower slider) 106a and a second slider (an upper slider) 106b slidably arranged along the rows 103 of elements.
Each of the left and right fastener stringers 102 include fastener tapes 107 having core thread portions 107a at opposite tape-side edges, and the rows 103 of elements formed by having a plurality of fastener elements attached to tape-side edge portions (element attachment portions) of the fastener tapes 107 including the core thread portions 107a. Stoppers 108 that prevent detachment of the second slider 106b are arranged at front ends of the left and right rows 103 of elements.
The box pin 104 is continuously extended from a rear end of the row 103 of elements arranged on the right fastener stringer 102. The box pin 104 includes a box pin body 111 that is fixed to a tape-end edge portion of the right fastener tape 107 including the core thread portion 107a, a stopper portion 112 that is arranged at a rear end portion of the box pin body 111 and stops the first slider 106a to prevent detachment of the first slider 106a, a first locking piece 113 having a triangular shape that is projected from the opposite surface of the insert pin 105 of the box pin body 111, and suppressing portions 114 that is formed on a front surface and a back surface of the base end portion at the row of elements side in the box pin body 111 and suppress sliding of the second slider 106b. 
According to the slide fastener 101 in Patent Document 1, the suppressing portions 114 are formed on a front surface and a back surface of the box pin body 111, as described above. Therefore, when the first slider 106a and the second slider 106b are lowered to an end position at a box pin 104 side along the rows 103 of elements and are held by the box pin 104, the suppressing portions 114 of the box pin 104 are brought into close contact with an inner surface of a slider body of the second slider 106b, and increase frictional force of the second slider 106b to the box pin 104.
Therefore, a relative position of the second slider 106b is stabilized, and free sliding of the second slider 106b is suppressed. Effects as explained below are obtained by this configuration.
For example, when the slide fastener 101 that can be reversely opened is used for a long coat or the like, the insert pin 105 and the box pin 104 of the slide fastener 101 are generally arranged at a position of a lower end portion of the front of the long coat. Therefore, when a person who wears the long coat closes the left and right fastener stringers 102, the person first lowers the first and second sliders 106a, 106b to an end position where the box pin 104 is arranged along the rows 103 of elements. Thereafter, the person inserts the insert pin 105 into an element guiding path of the first and second sliders 106a, 106b. 
At this time, the person reverses directions of the first and second sliders 106a, 106b by folding back a coattail of the long coat upward, to facilitate operation of inserting the insert pin 105 into the first and second sliders 106a, 106b. Further, the insert pin 105 is often inserted into the first and second sliders 106a, 106b in a state that the first and second sliders 106a, 106b are lifted to a position where the insert operation of the insert pin 105 becomes easy. In this case, a positional relationship of the first and second sliders 106a, 106b is reversed. Therefore, the insert pin 105 is inserted from lower sides of the first and second sliders 106a, 106b. 
However, when the box pin 104 and the first and second sliders 106a, 106b are lifted to a position where the insert operation of the insert pin 105 becomes easy as described above, the first slider 106a and the second slider 106b move downward due to own weight from a box-pin-side end position where the inert pin 105 can be inserted (hereinafter, “insert-pin inserting position”) and are deviated, when the first slider 106a and the second slider 106b are not supported with fingers.
When positions of the first and second sliders 106a, 106b are deviated from normal insert-pin inserting positions, the insert pin 105 is interfered with by the other row 103 of elements and the box pin 104 when inserting the insert pin 105 into the first and second sliders 106a, 106b, and there is inconvenience that the insert pin 105 cannot be sufficiently inserted to a predetermined position.
To overcome this inconvenience, according to the slide fastener 101 in Patent Document 1, the suppressing portions 114 are formed on the box pin 104 as described above. With this arrangement, the second slider 106b is held at the normal insert-pin inserting position by using frictional force between the suppressing portions 114 and the second slider 106b, and a relative position of the second slider 106b can be stabilized. At the same time, free sliding of the second slider 106b from the normal insert-pin inserting position can be suppressed.
Therefore, even when the person who wears the long coat lifts the box pin 104 and the first and second sliders 106a, 106b to a position where the insert operation of the insert pin 105 becomes easy by reversing the box pin 104 and the first and second sliders 106a, 106b before performing the insert operation of the insert pin 105, deviation of the first and second sliders 106a, 106b from the normal insert-pin inserting positions can be prevented. Accordingly, thereafter, when inserting the insert pin 105 into the first and second sliders 106a, 106b, the insert operation of the insert pin 105 can be performed smoothly.
Further, in Patent Document 1, a slide fastener 121 as shown in FIG. 17 is disclosed as other embodiment. The slide fastener 121 according to the other embodiment has a ridge portion 122 formed on the front surface and the back surface of the box pin body 111.
The ridge portion 122 is arranged closer to a front end of the box pin than the suppressing portions 114, such that the ridge portion 122 is brought into close contact with the inner surface of the slider body of the first slider 106a when the first slider 106a moves to the normal insert-pin inserting position where the first slider 106a stops at the stopper portion 112. With this arrangement, the first slider 106a is held at the normal insert-pin inserting position, and free sliding of the first slider 106a from the normal insert-pin inserting position is suppressed.
That is, according to the slide fastener 121 of the other embodiment, the suppressing portions 114 and the ridge portion 122 provided on the box pin 104 can suppress free sliding of the second slider 106b and the first slider 106a from the normal insert-pin inserting positions, respectively, and can stably hold the position of each slider.
Consequently, even when the person who wears the long coat lifts the box pin 104 and the first and second sliders 106a, 106b to a position where the insert operation of the insert pin 105 becomes easy by reversing the box pin 104 and the first and second sliders 106a, 106b before performing the insert operation of the insert pin 105, deviation of the first and second sliders 106a, 106b from the normal insert-pin inserting positions can be securely prevented. Accordingly, the insert operation of the insert pin 105 can be performed smoothly.